Coxsackievirus B plays a causal role in the etiology of type I, insulin- dependent diabetes mellitus (juvenile-onset diabetes). Isolates of the virus from diabetic children (diabetogenic strains) produce a diabetes-like disease in mice resulting in decreased insulin concentrations in the pancreas and serum, increased blood glucose concentrations, and impaired glucose tolerance. Type I diabetes in humans has an autoimmune basis. An islet cell autoantigen of molecular weight 64,000 (64K) is now considered to be a major target antigen of the autoimmune response. It appears that such a 64K autoantigen may also operate in the mouse system. The long-term objective of this research is to define the precise molecular mechanism by which this virus infection causes the insulin deficiency and produces diabetes. The specific aims for the period covered by this proposal are: (1) to characterize the 64K antigen and antibodies, and other beta cell proteins; and (2) to identify diabetogenic locus of the virus. A mouse model using diabetogenic and nondiabetogenic strains of coxsackievirus B4 is employed. The overall approach is to apply immunological and molecular biological techniques to fulfill these aspects of virus-induced diabetes. The antigen work will critically identify and characterize the protein, identify the conditions under which it is expressed in the virus-infected mice, determine the course of specific antibody development in these mice to correlate these antibodies with diabetes induction. In addition, viral antigens in the infected beta cells will be immunologically mapped. For diabetogenic locus identification, a collection of recombinant clones, containing the genes of two strains, will be constructed and tested for their diabetogenic potential. The selected recombinants will then be mapped and sequenced. The proposed study will augment our understanding of the trigger and pathway of the autoimmune response in virus-induced diabetes. This should lead to the development of rational strategies for the control and prevention of type I diabetes. Using data provided by this project, it may be possible to predict the virulence of human viruses from a knowledge of genetic structure.